Inhibitor



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Patented June 9, 1931 UNITED STATES Lxaunue PATENT OFFICE HARRY I. CORSON, 01: LAKEWOOD, OHIO,

GRASSELLI CHEMICAL OOMIPANY, 0F WARE ASSIGNOR, BY MISNE ASSIGNMENTS, TO THE CLEVELAND, OHIO, A CORPORATION OF DELA- INHIBITOR Ro Drawing.

The present invention relates to inhibitors, their use for controlling the action of acids upon metals, and to processes of cleaning, pickling, scaling or removing oxides and olther acid soluble deposits from metallic arti- 0 es.

I have found that thiuram sulfides display the property of inhibiting the action of acids upon base metals, that is to say, acids containing small amounts of my novel inhibitors will not, or only to a slight degree, dissolve such metals with correspondingly lesser evolution of hydrogen.

Thiuram sulfides are chemical compounds of the general formula in which R stands for hydrogen or a hydrocarbon radical and a: for one of the numerals, l, 2, 3, etc. They are easil roduced from the correspondingditl gcar amic afiids or their salts.

The usual pickling and cleaning baths for metallic articles consist of dilute mineral acids such as sulfuric or hydrochloric acid. The articles are treated therewith at various temperatures and under conditions suited to the particular problem, it being understood that pickling of sheet steel or of steel stock for wires, for instance, may require different operations, concentrations of acid, temperature, etc., than scaling boiler tubes or freeing water pipes from rust and other acid soluble incrustations.

The addition of asmall amount of a thiuram sulfide to the acids used in such operations will prevent or greatly reduce the attack of the acid on the metal itself, without materially affecting the dissolution of the scale, rust, and other incrustations. This results in a noticeable saving of acid, but the main advantage of the use of my novel inhibitors is the protection of the metal which is not weakened or pitted. Amounts of less than y, of 1% of a thiuram sulfide figured on the weight of the bath is usually sufficient to produce the desired inhibiting effect. Amongst the various thiuram sulfides I found that some of the best inhibitors will be found amongst the tetra-alkyl derivatives Application filed August 9, 1928. Serial No. 298,630.

su h as tetramethyl or tetraethyl thiuram sulfides.

I" The beneficial effect of my novel inhibitors Composition inhibitor No inhibitor used Thiuramdisulfidc..--- e Tetramethyl-thiuramo sulfi e measuring the gas plece of metal lmmersed in c. 0. Gas evolved in Amount use Home Hours Mixtures of my various inhibitors or mixtures of these with other known inhibitors can be used and similar improved results obtained.

These inhibitors can also be used in the presence of the foam-producing agents commonly added to pickling baths without detriment to the effect of either.

It will be understood that my invention is not limited to the particular substances and procedures mentioned herein, but that it comprises the application of my novel inhibitors to the various operations carried out under various conditions involving the action of acid upon metal articles where it is desired to free the metal from acid soluble incrustations with least possible attack of the metal itself.

I claim:

1. A pickling and cleaning bath for metcontaining a metal articles, the step comprising treating 106 2 r ad i M f 1. Hours C- ,I

Said articles with a dilute acid containing a small amount of a thiuram sulfide.

3. A pickling and cleaning bath for metals comprising a dilute acid containing a 5 small amount of a tetra-alkyl-thiuram sulfide. 4. A pickling and cleaning bath for metals comprising a dilute acid containing a small amount of a tetra-methyl-thiuram sulfide.

5. In a process for pickling and cleaning metal articles, the step comprising treating said articles with a dilute acid containing asmall amount of a tetra-alkyl-thiuram sulfide.

In a process for pickling and cleaning metal articles, the step comprising treating said articles with a dilute acid containin a small amount of a tetra-methylthiuram sulfide.

7. The process of pickling metals which comprises subjecting the metal to a pickling solution which contains a thiuram sulphide.

8. The process of cleaning a metal surface which comprises treating such metal with a sulfuric acid solution containing a small pro- -portion of a thiuram compound.

9. A pickling bath for iron and steel products comprising a pickle acid containing a dissolved thiuram compound.

In testimony whereof, I affix my signature.

HARRY P. CORSON. 3

Certificate of Correction Patent No. 1,809,621. Granted June 9, 193l,to

HARRY P. CORSON It is hereby certified that error appears in the printed specification of the abovenumbered patent requiring correction as followsaPage 1, strike out the table between lines and 7 5 and insert the following table instead:

Amount 0. 0. gas evolved in used Composition of inhibitor or 1 2 6 20 bath hour hours hours hours N ojnhibitor used 1, 010 2, 000

and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 25th day of August, D. 1931.

' M. J. MOORE,

[SEAL] i Acting Oomu'sstoner of Patents. 

